A verb form question with changing commas tests a verb’s job within the sentence. Sort the forms: a main verb says what a subject does; an -ing form needs a helper to do that. Then find the subject and read to the period to count its main verbs. Each clause, a subject with its verb, needs one main verb unless a joining word allows more. Cross out extra information to check the sentence, and match the commas around it.
Hints
- Hint 1
Read all the way to the period. Which word is the main verb for “Climate historian Annette”?
- Hint 2
Both uses of that introduce smaller parts of the sentence. Check who each verb belongs to instead of counting every verb you see.
- Hint 3
Cross out the stretch about the book’s early chapters and its argument. Can the words on either side form a complete sentence, and where does that stretch begin and end?
Step-by-step
Find the main verb, then mark off the description
Step 1Sort the forms and find the subject
Sort the verb forms in the choices: explores can be a main verb, while an -ing form needs a helper to be one. Who needs a main verb here? Climate historian Annette is the subject, so let’s look for the verb that says what she does.
- Step 2
Find Annette’s main verb
Keep reading until emphasizes that modern preparedness depends. What does Annette do? She emphasizes the need to understand past storms, which gives her a main verb after the blank. Mirror belongs to that today’s severe storms mirror patterns, where the storms are the subject, and depends belongs to the later that part, where preparedness is the subject. No joining word connects the blank to emphasizes, so the blank must describe Annette rather than add another main verb.
- Step 3
Find both ends of the description
The comma in medieval chronicles, emphasizes sits where the sentence returns to Annette’s main verb. What stretch could we cross out? The words about the book’s early chapters and its argument run from after Annette’s name through the chronicles. Removing them leaves a complete sentence about what Annette emphasizes, so the description needs a comma at each end.
- Step 4
Supply the describing form and opening comma
Annette looks into a compelling argument, so the -ing form describes what she’s doing: exploring. The comma after Gordon pairs with the comma in medieval chronicles, emphasizes, so Gordon, exploring gives us both the describing form and its opening mark. Choice B.